# Asymmetric Compensation of Reactive Power Using Thyristor-Controlled Reactors

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## Abstract

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## 1. Introduction

- No one on the market offers the SVC, which is based on TSCs and TCRs, for smooth asymmetric compensation of reactive power in low-voltage grids.
- There are few publications dedicated to the SVC for smooth compensation of reactive power in low-voltage grids [5,6,7,8,9,44]. However, all these publications are dedicated to symmetric compensation of reactive power in all three phases, and in most of them, just the simulation results are presented.

## 2. The Topology and Operation of the TCR Compensator

## 3. Investigation Results

#### 3.1. Investigation of the Compensator Based on a Single-Cored Three-Phase Reactor

_{L}and the approximate inductance of the coil can be obtained using the equation $L=\frac{{X}_{L}}{\omega}\approx 100mH$, where ω is the angular frequency of grid voltage. In order to avoid core saturation, the air-gaped core was used. To obtain the desired inductance of the reactor, the approximate design parameters of the reactor coil were chosen using the equation:

#### 3.2. Investigation of the Compensator Based on Separate Reactors for Every Phase

#### 3.3. Efficiency of the TCR Compensator

## 4. Conclusions

- TCR compensators, which typically are used in high- and medium-voltage utility grids, can be implemented in a low-voltage utility grid employing air-gapped reactors using a Y-connection connected to the neutral midpoint.
- Variation of the thyristor firing angle of one phase of single-cored three-phase reactor does not just change the reactive power of the controlled phase but influences the reactive power of phases with fixed firing angles. This fact shows that it is impossible to control the reactive power in every phase independently using a TCR compensator based on a single-cored three-phase air-gaped reactor, i.e., a compensator with such a reactor is not suitable for the asymmetric compensation of reactive power.
- Employment of three single-phase air-gaped reactors allows us to control the reactive power in every phase independently; therefore, a developed TCR compensator based on three single-phase reactors is suitable for smooth and asymmetric compensation of reactive power in a low-voltage utility grid.
- Commutation of the reactor using thyristor switches does not introduce any high-frequency disturbances of the reactor current and grid voltage.
- TCR compensator topologies with ∆ connection of coils of single-phase reactors as well as Y-connection with unconnected midpoint are not suitable for asymmetric compensation of reactive power in a low-voltage utility grid.
- The developed single-cored three-phase reactor and single-phase reactors are characterized by 0.955–0.975 efficiency.

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Block diagram of the thyristor-controlled reactor (TCR) compensator experimental test bench.

**Figure 4.**Dependences of reactive power consumed by the single-cored three-phase reactor on the firing angle of the thyristors.

**Figure 5.**The waveforms of the utility-grid phase voltage (violet) and the reactor current (cyan) on thyristor firing angle (α): (

**a**) 95° (

**b**) 110° (

**c**) 140° and (

**d**) 160°. Voltage zero crossing is displayed in yellow, thyristor control signal in green.

**Figure 6.**The spectrums of the reactor current at various thyristor firing angles: (

**a**) 95° (

**b**) 110° (

**c**) 140° and (

**d**) 160°. The frequency of the fundanental harmonic is 50 Hz.

**Figure 7.**Dependences of reactive power consumed by the single-cored three-phase reactor on the firing angle when the firing angle of one phase is variable and the angles of the remaining two phases are fixed. The Firing angle is variable for Phase 1 (

**a**,

**d**), for Phase 2 (

**b**,

**e**), for Phase 3 (

**c**,

**f**).

**Figure 8.**Dependences of reactive power consumed by the single-cored three-phase reactor on the firing angle when the firing angles of the two phases are variable and the angle of the remaining phase is fixed. The Firing angle is variable for Phase 1 (

**a**), for Phase 2 (

**b**).

**Figure 10.**Dependencies of reactive power consumed by the single-phase air-gaped reactors on the firing angle of thyristors.

**Figure 11.**Dependences of reactive power consumed by each single-phase air-gaped reactor on the firing angle when the firing angles of the two phases are fixed and the angle of the remaining phase is variable. The Firing angle is variable for Phase 1 (

**a**), for Phase 2 (

**b**).

**Figure 12.**Dependences of reactive and active power consumed by (

**a**) the single-cored three-phase reactor and (

**b**) three single-phase air-gaped reactors.

Parameter | Value |
---|---|

Relative magnetic permeability of iron core (μ_{I}) | 100 |

Number of turns of coil (N) | 510 |

Winding area (S) | 17.6 cm^{2} |

Length of coil (l) | 10.8 cm |

Wire cross-section | 1.8 mm^{2} |

Inductance of coil at core air gap length d = 0 | 530 mH |

Inductance of coil at d = 6 mm | 100 mH |

Inductance of coil at d = 10 mm | 37 mH |

Inductance of coil without core | 5.3 mH |

Thyristor Firing Angle (α) | Total Harmonic Distortion (THD), % |
---|---|

95° | 5.2 |

110° | 19.2 |

140° | 36.1 |

160° | 58.3 |

Parameter | Value |
---|---|

Relative magnetic permeability of iron core (μ_{I}) | 100 |

Number of turns of coil (N) | 160 |

Winding area (S) | 71.5 cm^{2} |

Length of coil (l) | 9.0 cm |

Wire cross-section | 3.1 mm^{2} |

Inductance of coil at core air gap length d = 0 | 256 mH |

Inductance of coil at d = 5 mm | 40 mH |

Inductance of coil at d = 10 mm | 18 mH |

Inductance of coil without core | 2.6 mH |

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## Share and Cite

**MDPI and ACS Style**

Šapurov, M.; Bleizgys, V.; Baskys, A.; Dervinis, A.; Bielskis, E.; Paulikas, S.; Paulauskas, N.; Macaitis, V.
Asymmetric Compensation of Reactive Power Using Thyristor-Controlled Reactors. *Symmetry* **2020**, *12*, 880.
https://doi.org/10.3390/sym12060880

**AMA Style**

Šapurov M, Bleizgys V, Baskys A, Dervinis A, Bielskis E, Paulikas S, Paulauskas N, Macaitis V.
Asymmetric Compensation of Reactive Power Using Thyristor-Controlled Reactors. *Symmetry*. 2020; 12(6):880.
https://doi.org/10.3390/sym12060880

**Chicago/Turabian Style**

Šapurov, Martynas, Vytautas Bleizgys, Algirdas Baskys, Aldas Dervinis, Edvardas Bielskis, Sarunas Paulikas, Nerijus Paulauskas, and Vytautas Macaitis.
2020. "Asymmetric Compensation of Reactive Power Using Thyristor-Controlled Reactors" *Symmetry* 12, no. 6: 880.
https://doi.org/10.3390/sym12060880